Automated machining systems and coordinate measurements systems require a precise means for locating surfaces on workpieces. One method of performing such measurement is to utilize a so-called "touch probe" in which a stylus is moved into a position where it touches the surface resulting in a movement of the stylus from its rest position.
The usefulness of these touch probes depends upon their capability of performing accurate repeatable measurements. It is often desirable to provide a probe that is capable of repeating its measurement to within about one micron or less. In other words, if the probe is used to make several measurements on the same workpiece surface, the calculated position thereof cannot deviate more than about one micron.
An important factor in maintaining accuracy of the probes performance is cleanliness. The probe is usually in an environment that includes metal chips and various chemical coolants and lubricants. Therefore the need to seal out dirt and contamination from the innerworkings of the probing device, such as that disclosed in U.S. Pat. No. 4,451,987 has been well established. The problem of providing a flexible, durable seal between the stylus holding-moveable member and the probe housing that does not interfere with probe accuracy and repeatability has, until this invention only been partially approached. The existing approaches for the protection from hot metal chips generated by the machining process are inadequate. Existing art provides an inner flexible diaphragm made of a flexible rubber or plastic material, appropriately convoluted to provide flexibility in the required directions. This type at seal must further be protected by something able to withstand direct contact with hot chips, dust and coolants found in todays machining centers and turning centers. One approach has been to provide a sliding, spherical member closely fitting the stylus holder-moveable member. The closeness of fit and resulting friction and random added on pretravel forces result in reduced repeatability and accuracy in the probe-seal system.
Those skilled in the art appreciate that the manufacture and assembly of probes of this type can be a difficult task. This can present problems which are not easily overcome. The entire probe must be constructed in such a manner that it is rugged and can be used over extended periods of time while also insuring that the accuracy of the probe measurement is not sacrificed. Thus, it is highly desirable to provide a probe construction that can be more easily manufactured while still achieving these high standards.